coming up, matt talks about that and more with mark zuckerberg. but first, natalie has more on the social network that has changed the world. >> it has. from the wall street debut to the launch of the time line, it's been a big year for facebook. and with the unprecedented billion member benchmark, it's inching closer to having all the friends in the world. >> reporter: it was 2004 when a 19-year-old named mark zuckerberg started a small website for college kids to share information. >> did you ever dream 2004 in your dorm room in harvard when you started this thing you'd end up sitting here one day and say we're going to cross 200 million users? >> no, i think that's a difficult thing to foresee. >> reporter: but today a benchmark as facebook announces it has 1 billion users, 1/7 of the world's population. >> facebook is an ecosystem. not only connects you to friends, not only connects yo uh to business opportunities, politicians are using it for their candidacy. it is huge. >> reporter: who is facebook's billionth friend? they joined on septembe